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The method of separation of chromate from high alkali medium by barium salt to get the intermediate product of barium chromate was proposed, and through the acid dissolution reduction method to get chromium hydroxide. Then, using the oxidability and acidity of hydrogen peroxide, it takes sodium hydroxide as a sodium source and accurately regulates the reaction conditions. The chromium hydroxide is directly oxidized to sodium chromate without by-products. The effects of reaction temperature, reaction time, liquid-solid ratio, stirring speed, quantity of hydrogen peroxide, and chromium alkali molar ratio have been studied, the reaction process was optimized by response surface method. The results showed that the optimal reaction alkali chromium molar ratio 2.15∶1（stoichiometric ratio）, liquid-solid ratio 3.9∶1 mL/g, theoretical multiple of hydrogen peroxide 1.86, temperature conditions were 88 ℃ and agitation speed of 300 r/min. Under this condition, the chromium oxidation rate can reach 99.56% for reaction 90 min. [ABSTRACT FROM AUTHOR]

Chromium exposure has adverse impacts on human health and the environment, whereas chromate-induced hepatotoxicity's detailed mechanism is still unclear. Therefore, the purpose of the current study was to reveal the crucial signaling pathways and genes linked to sodium chromate-induced hepatotoxicity. GSE19662, a gene expression microarray, was obtained from Gene Expression Omnibus (GEO). Six primary rat hepatocyte (PRH) samples from GSE19662 include sodium chromate-treated (n = 3) and the control PRH samples (n = 3). A total of 2,525 differentially expressed genes (DEGs) were obtained, especially 962, and 1,563 genes were up- and downregulated in sodium chromate-treated PRHs compared to the control. Gene ontology (GO) enrichment analysis suggested that those DEGs were involved in multiple biological processes, including the response to toxic substances, the positive regulation of apoptotic process, lipid and cholesterol metabolic process, and others. Signaling pathway enrichment analysis indicated that the DEGs were mainly enriched in MAPK, PI3K-Akt, PPAR, AMPK, cellular senescence, hepatitis B, fatty acid biosynthesis, etc. Moreover, many genes, including CYP2E1, CYP1A2, CYP2C13, CDK1, NDC80, and CCNB1, might contribute to sodium chromate-induced hepatotoxicity. Taken together, this study enhances our knowledge of the potential molecular mechanisms of sodium chromate-induced hepatotoxicity. [ABSTRACT FROM AUTHOR]

• A binary NaOH-NaNO 3 -H 2 O sub-molten system was proposed for the pressure oxidative leaching of chromite. • A high chromium extraction rate up to 99 % was obtained within 240 min under the optimal reaction conditions. • The addition of NaNO 3 served a dual role purpose: diluting the viscosity of the reaction medium and acting as an oxygen carrier. • During the 6 consecutive leaching reactions, the leaching rate of chromium was maintained around 97 %. The liquid-phase oxidation of chromite ore in sub-molten medium is regarded as a clean and efficient method for the preparation of chromate. However, its industrial application is limited by the need for specialized equipment, stringent reaction conditions, and complex chromate-alkali separation processes. To enhance the leaching of chromite and achieve milder reaction conditions, this study introduces a novel NaOH-NaNO 3 -H 2 O binary sub-molten salt reaction system. Effects of reaction parameters on the leaching ratio of chromium were systematically studied. The results showed that a high chromium extraction rate up to 99 % was obtained within 240 min under the optimal reaction conditions: a reaction temperature of 513.15 K, a NaNO 3 -to-ore mass ratio of 0.8:1, an alkaline-to-ore mass ratio of 4:1, an oxygen partial pressure of 2.0 MPa, a stirring speed of 800 rpm, and an alkali concentration of 50 wt%. Kinetics analysis revealed that the leaching process of chromite was controlled by the surface chemical reaction, with an apparent activation energy calculated as 31.58 kJ·mol−1. Moreover, it was also found that the addition of NaNO 3 in the reaction system served a dual role purpose: diluting the viscosity of the reaction medium and acting as an oxygen carrier, which significantly enhanced the leaching efficiency of chromium. Additionally, the binary reaction medium exhibited stable usage performance. During 6 consecutive leaching runs, a chromium leaching rate of around 97 % could be maintained. Therefore, the NaOH-NaNO 3 -H 2 O binary sub-molten system shows great potential for applications in the highly efficient leaching of chromite ore. [ABSTRACT FROM AUTHOR]

Gas turbine reliability is a crucial requirement for passenger safety in aviation and a secure energy supply. Hence, corrosive degradation of combustor parts, vanes, and blades in gas turbines must be prevented. One of the most severe forms of corrosion is alkali‐sulfate‐induced hot corrosion, which is associated with internal sulfidation of components and is usually anticipated to fade in importance in the absence of sulfur. However, the literature suggests that hot corrosion might still occur in low‐sulfur combustion gases. In this study, established thermodynamic modeling methods are used to analyze the low‐sulfur hot corrosion regime. Liquid sodium chromate is found to be stable in these conditions. A comparison of calculation results and engine findings suggests that high alkali levels can negatively impact thermal barrier coating life even if sulfur is absent in the fuel. Laboratory tests are carried out to validate the chromate formation on MCrAlY‐coated specimens. It is shown that molten sodium chromate can alter the oxidation behavior of MCrAlY, promoting the formation of voluminous spinel. This represents a new and different form of hot corrosion compared to type I hot corrosion. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of Cr6+ on the properties of alkali-activated slag cement (AAS), the effects of added dosage of Na2Cr2O4 on the setting time and compressive strength of AAS were measured. The leaching concentration of Cr6+ from AAS cement stone was measured using dual-beam UV-visible spectrophotometry. The effect of Na2Cr2O4 on the hydration kinetics of AAS cement was monitored by microcalorimetry and the corresponding kinetic parameters were analyzed. The pore solution from AAS was collected and analyzed using the high pressure press method. The effects of Na2Cr2O4 on the hydration products of AAS cement were observed and compared using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results showed that the AAS hydration process was markedly affected by Na2Cr2O4 dosage. The setting time of AAS pastes was increased and the compressive strength of cement stones was reduced with increasing dosage of Na2Cr2O4. With the development of AAS hydration, the leaching concentration of Na2Cr2O4 gradually decreased. Na2Cr2O4 did not affect the dissolution of slag particles, but impeded the formation of C-S-H gel. The Cr6+ was immobilized chemically in the form of needle-like CaCrO4 particles formed by the chemical reaction between Na2Cr2O4 and Ca2+ leaching from the slag.

Sukinda overburden is dumped with chromite ore tailing which contains about 17% Cr2O3. The other constituent with overburden is iron, silica and alumina. Because of its complex nature and large amount of gangue material it is not suitable for the extraction of valuable chromium by conventional route. The author of the present investigation has tried to recover chromium as sodium chromate from chromite overburden. In this investigation the ore is mixed with sodium carbonate. The mixture is heated in a raising hearth furnace at 1123 K. Before roasting, TG/DTA analysis has been done to fix the operating temperature. After roasting at 90 min, the roasted product is ground and sieved. The rate-determining step of roasting for the conversion into sodium chromate has also been investigated and it shows that the required activation energy at the temperature range 923–1123 K is 60 kJ/mole. The roasted product is leached in hot water condition at an optimum pulp density of 1:5 to obtain the chromium recovery. After leaching, solid liquid separation is done. The leach liquor containing sodium chromate is vaporized and a bright yellow crystal of sodium chromate is obtained. A recovery of 85% chromium is obtained at the optimum condition and the purity of sodium chromate is found to be 99.5%. This chromate is suitable for the use in chemical and tanning industries. A portion of ore, roasted product and leached residue are subjected to XRD and EPMA studies to know the mode of conversion and phases present in different stages of reaction. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of floral spectral studies on 1275 flowers from India, Brazil, Israel, Germany, and Norway. Floral spectral reflectance from 400 to 700 nm (nm) was used to quantitatively represent 'human-perceived' color of flowers in Red, Green, Blue color space. Floral spectral reflectance from 350 to 600 nm was used to discern and objectively represent 'insect pollinator-perceived' flower colors in color hexagon. We leverage the advantage offered by 'quantified human perception' provided by 'human-perceived' floral colors to represent the distribution of floral hues and uncover the relationship between the composition of incoming solar radiation and predominant 'human-perceived' floral colors at the tropics and the higher latitudes. Further, the observed species-level mutual exclusivity of 'insect pollinator-perceived' floral colors is stated as chromatic exclusivity hypothesis. We compare 'human-perceived' and 'insect pollinator-perceived' floral colors at Trivandrum (India) and provide a physical explanation for short and long 'wavelength triads' of insect pollinator and human visual sensitivity respectively. Highlights • Objective representation of human and insect pollinator perceived floral colors. • Reports the mutual exclusivity of insect pollinator-perceived floral colors. • The composition of the incoming solar spectrum determines the floral colors. • Floral radiometry will complement the development of national pollinator strategies. [ABSTRACT FROM AUTHOR]

Solid solutions of Na2SO4/Na2CrO4 are studied using laser Raman spectroscopy, infrared spectroscopy and differential scanning calorimetry. When the chromate ion concentration increases, the lattice expands continuously and a higher temperature sulfate phase, phase III, is stabilized to room temperature. The site group and correlation field splitting are also studied as a function of the relative sulfate\chromate ion concentration. The transition enthalpy from phase III to a higher temperature sulfate phase, phase I, has been measured. The calculated transition entropy is perfectly explained by a mixing entropy model. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A safe, economical treatment of hazardous chromium-bearing vanadate residue (CVR) will significantly benefit the clean production of chromate-bearing salts. This study investigated recovery of sodium vanadate and sodium chromate from CVR in sodium bicarbonate solution. Results indicate that the stability of calcium vanadate and calcium chromate depends on pH and [HCO3-]. CaV2O6·4H2O transforms into CaV2O6·4H2O, CaV2O6·2H2O, CaV2O6, Ca2V2O7·2H2O, and Ca5(VO4)3(OH) when pH increases from 7.51 to 12.32. Increasing pH and reducing CVR dosage improve the vanadate extraction rate, and high V2O5 and Na2Cr2O7·2H2O extraction rates are achieved in dilute NaHCO3 solution. Moreover, addition of NaOH positively contributes to the recovery of vanadate and chromate from CVR. Over 95% V2O5 and Na2Cr2O7·2H2O in CVR can be extracted from 60 g/L NaHCO3 and 30 g/L NaOH solutions at 90 °C for 2 h. In order to reduce the hazardous residue containing chromate after recovery of CVR, calcium circulation is presented. Results show that more than 60% lime can be saved with fresh residue addition to remove vanadate from sodium chromate solution due to the active CaCO3. Moreover, no lime is required in removal of vanadate when the roasting residue is added. Therefore, a novel process is developed for utilization of CVR. [ABSTRACT FROM AUTHOR]

The paper presents a new concept of metallic materials containing inhibitor, able to inhibit corrosion as it initiates. Al particles with uniformly dispersed sodium chromate (0.5–20 wt%) were produced by high-energy ball milling followed by cold compaction. Cyclic potentiodynamic polarization tests and surface analysis after constant immersion tests revealed a significant improvement in corrosion behavior due to the sodium chromate addition up to 5 wt%. Improved corrosion behavior was attributed to the release of inhibitor as corrosion occurred. X-ray photoelectron spectroscopy indicated presence of the Cr 3+ in the passive film. [ABSTRACT FROM AUTHOR]

It is essential to control silica levels in sodium chromate solution during the process of electrolytic synthesis of sodium dichromate. On the basis of previous work, the desilication conditions were systematically studied and pH was found to have the most serious impact on the desilication process. The desilication rate under optimal conditions obtained from the orthogonal experiment results was up to 99.3%. Kinetic experiments showed that the desilication reaction was first-order in SiO2 concentration and the apparent activation energy was calculated to be 22 kJ mol-1, which is far less than the reported values. The morphology and structure of the desilication reaction product (DSP) were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). SEM showed that DSP had a loose etched structure. The pattern of XRD illustrated the crystallinity of DSP increased along the duration of the experiment. The phase of DSP was mainly Na6(AlSiO4)6. Based on the experimental data, the desilication mechanism has been discussed. The hexameric aluminosilicate ions were produced by the reaction of monomeric aluminosilicate ion, through hydrogen bond interaction, which was formed by SiO2(OH)22- and Al(OH)4-. [ABSTRACT FROM AUTHOR]

In this work, porous anodic oxides were produced by traditional and modified tartaric sulfuric anodizing (TSA) processes and sealed in hot water, chromate and cerium based solutions. The sealing behavior of a film with relatively coarse porosity, generated at high voltage (traditional TSA), was compared to the sealing behavior of a film with finer porosity and generated at reduced potential (modified TSA). After sodium chromate sealing, the two anodizing cycles produced film with similar anticorrosion performance. Conversely, after hot water or cerium sealing, the finer oxides generated at low voltage (modified TSA) provided much better corrosion resistance. EIS performed in-situ during sealing revealed that chromate sealing is very aggressive to the porous skeleton compared to the other sealing treatments. Therefore, the original morphology has little effect on the final performance, since both fine and coarse oxides are substantially attacked. In contrast, the oxide morphology has a substantial effect when sealing is performed in hot water or cerium-based solution. Overall, it is possible to obtain films with anticorrosion performance equivalent or improved compared to that obtained by traditional TSA anodizing cycle sealed with chromate by combining the low voltage anodizing cycle with the cerium-based sealing. [ABSTRACT FROM AUTHOR]

Solubility and metastable zone width (MSZW) of aqueous sodium dichromate solutions in different concentration of sodium chromate were studied experimentally by the polythermal method using a turbidity monitoring technique. The effects of cooling rate R , saturation temperature T 0 of sodium dichromate and concentration c i of sodium chromate on the MSZW were studied. The results show that the MSZW widens with increasing cooling rate R but it narrows with increasing saturation temperature T 0 of sodium dichromate and concentration c i of sodium chromate. The experimental data were analyzed by using an equation, based on the classical three-dimensional nucleation theory, relating MSZW with cooling rate R . [ABSTRACT FROM AUTHOR]

Chromic acid anodizing has been used for almost a century to enhance corrosion protection of aerospace alloys. For some applications, hydrothermal sealing in hexavalent chromium-containing solution is required to enhance further the corrosion resistance but, due to environmental concerns, the use of hexavalent chromium must be discontinued. Good progress has been made to replace chromates during anodizing but comparatively less effort has focused on the sealing process. In this work, for the first time, electrochemical impedance spectroscopy (EIS) has been used to characterize in-situ the sealing processes occurring during hot water sealing, sodium chromate sealing and cerium sealing. The results suggest that the processes occurring during sodium chromate sealing are significantly different compared to hot water and cerium sealing. In particular, during chromate sealing, the porous skeleton is significantly attacked, suggesting that the anticorrosion performance is likely to arise from the residuals of chromate rather than from the improvement of the barrier properties. In contrast, during hot water sealing, little attack occurs on the porous skeleton, and the improved corrosion protection is due to the enhanced barrier effect. During cerium sealing, precipitation of cerium products occurs, providing an inhibitor reservoir, and little, if any, attack occurs on the pre-existing oxide. [ABSTRACT FROM AUTHOR]

Reduction of chromium (VI) from Na 2 CrO 4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na 2 CrO 4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na 2 CrO 4 to metallic Cr attained 96.16% efficiency. Al 2 O 3 –Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al 2 O 3 –Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al 2 O 3 –Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment. [ABSTRACT FROM AUTHOR]

Charge-discharge properties of sodium-ion batteries using the Na[FSA]-[CCpyrr][FSA] (FSA: bis(fluorosulfonyl)amide, CCpyrr: N-methyl- N-propylpyrrolidinium) ionic liquid were investigated over a temperature range of 273-363 K. NaCrO and hard carbon (HC) were used as positive electrode and negative electrode active materials, respectively, and their fundamental charge-discharge characteristics were examined with coin-type half-cells. A 1.5 mAh coin-type full cell composed of HC/NaCrO showed excellent cycle properties, maintaining 90 % of its initial capacity after 1000 cycles at 333 and 363 K. The 1.5 mAh full cell also exhibited a high charge-discharge energy efficiency of 97.5 % at 363 K and C/5 rate. A large-sized prismatic HC/NaCrO full cell with a capacity of 27 Ah was fabricated by a mass production process, and its performance was confirmed to be comparable with that of the 1.5 mAh coin-type cell. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

To realize the effective separation of Na 3 VO 4 , Na 2 CrO 4 and the impurity Na 2 CO 3 in a newly developed vanadium production process using concentrated alkaline solution as reaction media, the equilibrium liquid phase solubility and solid phase compositions of the NaOH–Na 3 VO 4 –Na 2 CrO 4 –Na 2 CO 3 –H 2 O system at (40 and 80) °C were measured. The obtained solubility data were afterwards compared with quaternary NaOH–Na 3 VO 4 –Na 2 CrO 4 –H 2 O subsystem to investigate the salting-out effect of Na 3 VO 4 , Na 2 CrO 4 and Na 2 CO 3 . Further, a strategy for effective separation of Na 3 VO 4 and Na 2 CrO 4 from the NaOH–Na 3 VO 4 –Na 2 CrO 4 –Na 2 CO 3 –H 2 O pentabasic system has been proposed on the basis of detailed analysis of crystallization zones. [ABSTRACT FROM AUTHOR]

The effects of food supplementation with sodium chromate at concentrations of 1–500 μM on development of Drosophila melanogaster larvae and food intake, carbohydrate and lipid pools in adult fruit flies were investigated. Food supplementation with hexavalent chromium (Na 2 CrO 4 ) at high concentrations delayed larval development and decreased the percentage of larvae that pupated which indicated a relatively low toxicity. The supplement decreased glucose levels in fly hemolymph, but at concentrations of 5–25 μM increased fly carbohydrate reserves: hemolymph trehalose and whole body trehalose and glycogen. The data on parameters of carbohydrate metabolism show that chromate possesses some insulin-mimetic properties. The changes in metabolism of carbohydrates under chromate exposure were also accompanied by an increase in total lipid levels and in the portion of triacylglycerides among all lipids. Chromate addition to fly food did not affect male or female body mass, but reduced food consumption by females at all concentrations used, whereas in males only 500 μM chromate decreased food consumption. The data show that: (1) Cr 6 + has many of the same effects as Cr 3 + suggesting that it might be just as effective to treat diabetic states, likely as a result of intracellular reduction of Cr 6 + ions, and (2) the Drosophila model can be used to develop new approaches to investigate the molecular mechanisms of chromium as an insulin-mimetic. Although it is usually believed that hexavalent chromium possesses higher toxicity than the trivalent ion, due to its easier penetration into the cell, application of hexavalent chromium may substantially decrease the chromium doses needed to get the desired effects. [ABSTRACT FROM AUTHOR]

Thesolubility of sodium chromate tetrahydrate has been investigatedin the temperature range from 290.15 K to 325.15 K using the conventionalpolythermal method by means of the laser technique. The metastablezone width (MZW) and the apparent nucleation order of sodium chromatetetrahydrate were calculated. The effects of cooling rate, initialcomposition, stirring rate, and seed particles on the MZW were alsostudied. The results show that the MZW of sodium chromate tetrahydratefirst increases and then narrows with increasing initial composition.The MZW becomes wider by reducing the cooling rate and the mass ofseed particles, whereas the MZW will be reduced by enhancing the rotationfrequency of stirring and the diameter of seed particles. [ABSTRACT FROM AUTHOR]

Abstract: Particles of Fe2Al5 (60–211μm diameter) were leached at 10, 30 and 50°C in 3M NaOH containing varying amounts of sodium chromate in the range 0.005–0.05M. The kinetics of leaching was fitted to solid-state kinetic models. The model best fitting the data was the Avrami–Erofeev model −ln(1− α)1/1.5 = kt. Apparent activation energies were in the range 60–63kJmol−1. The BET surface areas of the promoted materials were high, with values in the range 57–91m2 g−1. Catalysts were tested for the water–gas-shift (WGS) reaction at 350°C and it was found that the chromium content of the catalysts had a significant effect on the WGS activity, which went through a maximum for a catalyst containing around 2wt% chromium. [Copyright &y& Elsevier]

Two model chromium (Cr) compounds, one hexavalent (sodium chromate) and one trivalent (chromium chloride), were investigated in a human lymphoblastoid cell line (TK6) to increase our knowledge regarding Cr-induced genotoxicity mechanisms. Both selected compounds were genotoxic using the comet assay, although the percentage of DNA in tail obtained after treatment with CrVI was significantly higher than that obtained with CrIII, at the higher concentrations tested. To determine the nature of the induced damage, enzymes recognizing oxidized bases were used. Treatments with formamidopyrimidine (FPG) and endonuclease III (EndoIII) displayed a greater degree of DNA damage, indicating that the induction of oxidized bases accounts for an important proportion of the damage induced by Cr compounds. In addition, the kinetic repair studies showed that generated DNA damage is removed in approximately 8 h, with the damage induced by CrIII being removed/repaired more rapidly than damage produced by CrVI. To detect Cr interferences with the repair process, a post-treatment was applied after exposure to 2 Gy gamma radiation. Post-treatment significantly delayed the repair kinetics of DNA damage induced by radiation. This interference effect induced by CrVI was more pronounced. In conclusion, evidence indicates that a high proportion of the Cr-induced DNA damage is correlated with oxidative damage, and that both Cr compounds interfere with repair mechanisms involved in repair of DNA damage induced by gamma radiation. [ABSTRACT FROM AUTHOR]

The article focuses on the application of multi-criteria analysis and technological quality method to evaluate variants of the process of sodium chromate production from chromic waste material. It explains how these methods permit a complex assessment of the environmental effects and economic impact of modernized technological solutions. The results of the analysis indicated that the most advantageous variant for sodium chromate production involved off-site recycling of chromic tannery waste and on-site recycling of waste from old chromic heaps.

One of the milestone structures in the development of transition-metal complexes with metal-metal bonds of multiple bond order was the lithium methylchromate dimer MegCr2(Li(donor)]4 (donor = THF or Et2O). Using a simple salt metathesis reaction mixing this compound with sodium tert-butoxide, the sodium congener Me8Cr2[Na(OEt2)]4 has been synthesized as a green crystalline compound and isolated in 51% yield. Its solid-state structure was determined by single-crystal X-ray diffraction. Exhibiting exact crystallographic C4h symmetry, this heavier alkali-metal chromate structure is also dimeric, formally comprising a (Me8Cr4)4- tetranionic core with four peripheral Na+ cations carrying supporting ether ligands. Its salient feature is the long Cr⋯Cr distance of 3.263(2) Å, which is remarkably elongated compared to that in the lithium THF-solvated congener [1.968(2) Å]. With respect to the methyl C atoms, the Cr coordination is distorted-square-planar. Each Na+ interacts with four methyl C atoms, and there are also some short Na⋯ H(C) contacts. Unlike for lithium chromate, no NMRspectroscopic data could be obtained for sodium chromate. The paramagnetic character of sodium chromate was confirmed by variable-temperature magnetization measurements, which indicated antiferromagnetic behavior. [ABSTRACT FROM AUTHOR]

The objective of this investigation was to recover chromium as sodium chromate of 99.5% purity from stainless steel dust. The dust contains 7.72% chromium obtained from stainless steel processing plants. The stainless steel dust mostly contained iron in oxide form along with chromium, nickel (1.71%) and manganese (3.55%). The steel dust was roasted with soda ash followed by water leaching to recover the major constituent chromium. It was found that roasting at 1073 K for 90 minutes resulted in maximum (95%) chromium recovery. Kinetics of sodium chromate formation followed a topochemical model involving chemical reactions at the surface with activation energy of 39 kJmol-1. TG/DTA, XRD phase identification and SEM microphotographs confirmed the experimental observation and the mode of reaction. [ABSTRACT FROM AUTHOR]

To explicate the thermodynamics of the chromite ore lime-free roasting process, the thermodynamics of reactions involved in this process was calculated and the phrases of sinter with different roasting times were studied. The thermodynamics calculation shows that all the standard Gibbs free energy changes of the reactions to form NaCrO, NaO·FeO, NaO·AlO and NaO·SiO via chromite ore and NaCO are negative, and the standard Gibbs free energy changes of the reactions between MgO, FeO and SiO released from chromite spinel to form MgO·FeO and MgO·SiO are also negative at the oxidative roasting temperatures (1 173-1 473 K). The phrase analysis of the sinter in lime-free roasting process shows that NaO·FeO, NaO·AlO and NaO·SiO can be formed in the first 20 min, but they decrease in contents and finally disappear with the increase of roasting time. The final phase compositions of the sinter are NaCrO, MgO·FeO, MgO·SiO and MgO. The results indicate that NaCrO can be formed easily via the reaction of NaCO with chromite ore. NaO·FeO, NaO·AlO and NaO·SiO can be formed as intermediate compounds in the roasting process and they can further react with chromite ore to form NaCrO. MgO released from chromite ore may react with iron oxides and silicon oxide to form stable compounds of MgO·FeO and MgO·SiO, respectively. [ABSTRACT FROM AUTHOR]

Hexavalent chromium is a marine pollutant of concern, both for the health of ocean ecosystems and for public health. Hexavalent chromium is known to induce genotoxicity in human and other terrestrial mammals. It is also known to be present in both water and air in the marine environment. However, currently there are limited data concerning both chromium levels and its toxicological effects in marine mammals. This study investigated the cytotoxic and genotoxic effects of soluble and particulate hexavalent chromium in sperm whale skin fibroblasts. Both forms of hexavalent chromium induced concentration-dependent increases in cytotoxicity and genotoxicity indicating that these compounds can be a health risk if the whales are exposed to them. These data support a hypothesis that chromium is a concern in the marine environment in general and for the health of sperm whales in particular. Environ. Mol. Mutagen. 52:43-49, 2011. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The virulence of Candida species depends on many environmental conditions, including extracellular pH and concentration of alkali metal cations. Tests of the tolerance/sensitivity of four pathogenic Candida species ( C. albicans, C. dubliniensis, C. glabrata, and C. parapsilosis) to alkali metal cations under various growth conditions revealed significant differences among these species. Though all of them can be classified as rather osmotolerant yeast species, they exhibit different levels of tolerance to different salts. C. parapsilosis and C. albicans are the most salt-tolerant in general; C. dubliniensis is the least tolerant on rich YPD media and C. glabrata on acidic (pH 3.5) minimal YNB medium. C. dubliniensis is relatively salt-sensitive in spite of its ability to maintain as high intracellular K/Na ratio as its highly salt-tolerant relative C. albicans. On the other hand, C. parapsilosis can grow in the presence of very high external NaCl concentrations in spite of its high intracellular Na concentrations (and thus lower K/Na ratio) and thus resembles salt-tolerant (halophilic) Debaryomyces hansenii. [ABSTRACT FROM AUTHOR]

The osmotic coefficients of the Na2CrO4−H2O system at 353.15 K were determined using isopiestic method ranging from 0.05 to 7.683 mol·kg−1. The experimental osmotic coefficients were excellently correlated with Pitzer equation to obtain the interaction parameters, the activity coefficients, and the solubility product for Na2CrO4. Furthermore, the solubility of Na2CrO4in NaOH solutions at 353.15 K was predicted using binary parameters, and the predicted values agree with the experimental data, demonstrating the Pitzer equation is capable of optimizing the processes for the removal and recovery of sodium chromate in NaOH solutions at high temperature. [ABSTRACT FROM AUTHOR]

Abstract: Currently, 80–90% of leather production uses chromium tanning; thus, the trimmings and shavings resulting from the manufacturing of leather goods create a waste with a high pollution potential. One alternative for handling this scrap-leather waste is thermal treatment (gasification and combustion). The ashes generated during this process are rich in chromium, containing between 50% and 60% chromium oxide (Cr2O3) by mass, and the ashes can thus potentially be utilized as a source of chromium for the synthesis of sodium chromate (Na2CrO4). With the aim of improving on the results of previous attempts made to recover chromium from these ashes, in this work, the use of sodium nitrate to oxidize the trivalent chromium to the hexavalent form was studied. The resulting conversion of chromium (III) to chromium (VI) achieved was over 94%, and the sodium chromate obtained from the ashes showed physical properties similar to the commercial product. [Copyright &y& Elsevier]